Chemosensory signals activate brain regions along the vomeronasal and main olfactory pathways. In male hamsters, socially relevant chemosignals.from the same species of animal (conspecific) activate the anterior medal amygdala (MeA) and the posterior medial amygdala (MeP) and do not activate the GABATergic intercalated nucleus (ICN). Socially non-relevant chemosignals from other species activate MeA and ICN, but fail to activate MeP. Oxytocin knockout mice (OTKO) fail to recognize a conspecific that they have encountered previously. The cFos patterns in the medial amygdala suggest a heterospecific-like response to the stimulus animal. Therefore it is possible that oxytocin (OT) mediates the signal from the vomeronasal system in the medial amygdala allowing for "downstream" continuation of the signal. These and other data suggest that oxytocin (OT) may affect medial amygdala responses to socially-relevant and socially nonrelevant stimuli differently. This proposal will investigate OT effects in medial amygdala in response to conspecific and heterospecific chemosensory stimulation.